US3688023A - Color television camera - Google Patents

Color television camera Download PDF

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Publication number
US3688023A
US3688023A US137334A US3688023DA US3688023A US 3688023 A US3688023 A US 3688023A US 137334 A US137334 A US 137334A US 3688023D A US3688023D A US 3688023DA US 3688023 A US3688023 A US 3688023A
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United States
Prior art keywords
color
transparent conductive
conductive layer
layer
layers
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Expired - Lifetime
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US137334A
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English (en)
Inventor
Hiromichi Kurokawa
Yasuharu Kubota
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Sony Corp
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Sony Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/26—Image pick-up tubes having an input of visible light and electric output
    • H01J31/46—Tubes in which electrical output represents both intensity and colour of image
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/01—Circuitry for demodulating colour component signals modulated spatially by colour striped filters by phase separation

Definitions

  • a color television camera comprises an image pickup tube having a photoconductive layer for the photoelectric conversion of images projected thereon into an electrical output, a color filter for forming a color separated image of an object to be televised on the photoconductive layer, and an electrode arrangement through which an index image can be electrically produced on the photoconductive layer to provide in the tube output an index signal as'well as a color video signal corresponding to the color separated image, such electrode arrangement including a first continuous transparent conductive layer and a second transparent conductive layer in the form of spaced stripes on the first transparent conductive layer and electrically insulated from the latter, with the photoconductive layer contacting the electrode arrangement at the stripes of the second transparent conductive layer and at the areas of the first transparent conductive layer 9Claims, 16Drawing Figures 7111 '23,: Hill PATENTED M1929 I97? 3 688, 023
  • the present invention relates generally to color television cameras, and more particularly is directed to improvements in a color television camera of the type employing an image pickup tube which generates a composite signal composed of an index signal and a color video signal, for example, as disclosed in copending US. Pat. application Ser. No. 72,593, filed Sept. 16, 1970, by Yasuharu Kubota, one of the present inventors, and having a common assignee herewith.
  • a color television camera in the identified application, includes a single image pickup tube having a photoconductive surface which is scanned for the photoelectric conversion of images projected thereon into an electrical output, a color filter for forming a color separated image of an object to be televised on the photoconductive surface, and an electrode arrangement by which an index image is electrically produced on the photoconductive surface to provide, in the tube output, an index signal as well as a color video signal corresponding to the color separated image.
  • the index signal as thus produced, can be conveniently employed for separating individual color component signals from the color video signal, certain problems do exist in respect to the electrode arrangements specifically disclosed in the identified prior application.
  • the electrode arrangement is disclosed to include two interleaved striped electrodes insulated from each other, signals are not obtained at the tube output when scanning those portions of the photoconductive surface located between the striped electrodes.
  • an additional electrode is disclosed as being effective to avoid such interruption of the signal output, this introduces complexity and increased costs in the manufacture of the image pickup tube.
  • the electrode arrangement in a color television camera of the described type, includes a first continuous transparent conductive layer and a second transparent conductive layer in the form of spaced stripes on the first layer and electrically insulated from the latter, with the photoconductive layer contacting the electrode arrangement at the stripes of the second transparent conductive layer and at the areas of the first transparent conductive layer between such stripes.
  • FIG. 1 is a schematic diagram showing one example of a color television camera according to this invention
  • FIG. 2 is an enlarged cross-sectional view of the principal portion of an image pickup tube employed in the camera of FIG. 1;
  • FIG. 3 is an enlarged elevational view illustrating the principal portion of the image pickup tube as viewed from the interior of the latter with its photoconductive layer removed;
  • FIGS. 4 and 5A-5F are waveform diagrams to which reference will be made in explaining this invention.
  • FIG. 6 is a frequency spectrum diagram for explaining this invention.
  • FIGS. 7A and 7B are enlarged, cross-sectional views illustrating steps involved in the manufacture of the principal portion of the image pickup tube.
  • a color television camera according to thisinvention comprises two sets of electrodes A and B disposed adjacent the photoconductive layer 1 of a pickup tube 2.
  • the photoconductive layer 1 is formed, for example, of materials such as antimony trisulfide, lead oxide, and the like, and the electrodes A and B are transparent conductive layers formed, for example, of tin oxide including antimony.
  • the electrode A is a continuous transparent conductive layer formed on a glass plate 3, which is connected to a terminal T On the electrode A there are formed transparent, spaced apart striped insulating layers 5, for example, of silicon dioxide, and, on such striped insulating layers, transparent electrode stripes B B B, B which together constitute the striped electrode B connected to a terminal T,,.
  • the several striped insulating layers 5 and the electrode stripes B,,B B B, are connected to each other at both of their ends, as particularly shown on FIG. 3.
  • elongated open or slot-like areas or gaps 6 are defined between adjacent striped insulating layers 5 and the respective stripes of electrode B, and such slot-like areas or gaps 6 are made to extend perpendicular to the horizontal scanning direction of an electron beam in tube 2.
  • the photoconductive layer 1 is shown to make direct contact with the electrode A in gaps 6 and with the striped electrode B in the order A,B ,A,B A,B,, A,B,, in the horizontal scanning direction of the electron beam.
  • the width of each of the stripes of electrode B and the width of each slot-like area or gap 6 is about 35 microns
  • the thickness D of the photoconductive layer 1 is about 1.0 micron
  • the thicknesses of the electrodes A and B and of the insulating layer 5 are about 0.2 microns and from 0.4 to 0.5 microns, respectively.
  • the electrodes A and B and photoconductive layer 1 are shown to be at one side of a glass plate 3.
  • an optical filter F made up of red, green and blue color filter elements or stripes F F and F arranged in a repeating cyclic order of F ,F ,F ,F ,F ,F
  • the color filter stripes are disposed parallel to the length of the stripes of electrode B in such a manner that each triad of red, green and blue color filter elements F F and F is opposite to a pair of adjacent electrodes A and B,. So long as the electrode B and the optical filter F are aligned with each other in their longitudinal directions, their relative lateral arrangement is not critical.
  • the optical filter F is fixed on the inner surface of the face plate 4 which closes one end of the envelope 2E of tube 2. Thus, filter F, plate 3, electrodes A and B photoconductive layer 1 are enclosed in the tube envelope.
  • a transformer 12 which consists of a primary winding 12a and a secondary winding 12b having a mid tap t and end terminals t and t which are respectively connected to the terminals T and T of the image pickup tube 2.
  • the primary winding 12a is connected to a signal source 13 which produces an alternating signal S, that is synchronized with the line scanning period of the image pickup tube 2.
  • This alternating signal S has a rectangular waveform, for example, as illustrated in FIG. 4, with a pulse width equal to a horizontal scanning period H of the electron beam, for instance, a pulse width of 63.5 microseconds and a frequency which is one half of the horizontal scanning frequency, that is, 15.75/2 z.
  • the mid tap 1 of the secondary winding 12b of the transformer 12 is connected to the input of a pro-amplifier 15 through a capacitor 14 and is suppoied with a DC bias voltage of 10 to 50V from a power source B+ through a resistor R.
  • the electrodes A and B are alternately supplied with voltages that are higher and lower than the DC bias voltage for every horizontal scanning period, so that a striped potential pattern corresponding to the electrodes A and B is formed on the surface of the photoconductive layer 1. Accordingly, when the image pickup tube 2 is not exposed to light, a signal corresponding to the rectangular waveform illustrated in FIG. 5A is derived at the mid tap t due to electron beam scanning in a scanning period Hi.
  • a DC bias voltage for example, of 30V
  • an alternating voltage of 0.5V is impressed between the terminals T and T a current flowing across the resistor R varies by 0.05 microamperes and can be used as an index signal.
  • the frequency of this index signal S may be determined with reference to the width and interval of the electrodes A and B and one horizontal scanning period of the electron beam, and, for example, may be 3.5 8Ml-Iz.
  • signals corresponding to the light intensity of the filtered red, green and blue components are produced on the photoconductive layer 1 in overlapping relation with the index signal S, to produce a composite signal S, for example, as illustrated in FIG. 5B, in which the reference characters R, G and B respectively designate portions of the composite signal S, corresponding to the red, green and blue color components.
  • the frequency spectrum of the composite signal 8,, as illustrated in FIG. 6, is determined by the width of the electrodes A and B, the width of repeat of the optical filter F and the horizontal scanning period. Therefore, the composite signal S is, in its entirety, in a bandwidth of 6 MHz and the luminance and chrominance signals Sy and S are respectively arranged in the lower and higher bands. It is preferred to minimize overlapping of the luminance and chrominance signals S, and S and, if desired, for this purpose, a lenticular lens or the like may be disposed in front of the image pickup tube 2. This optically reduces resolution and narrows the luminance signal band.
  • Such a composite signal S, (or S,') is first supplied to the pro-amplifier 15, to be amplified therein, and is then supplied to a process amplifier 16 for waveform shaping and/or gamma correction. Thereafter, the signal is applied to both a low-pass filter l7 and a bandpass filter 18.
  • S and S,, are low frequency components or fundamental components of the chrominance signal S, and the index signal 8,, respectively.
  • the separation of these signals is achieved in the following manner without using a filter.
  • Reference numeral 19 indicates a delay circuit, such as, for example, an ultrasonic delay line, by means of the signal S3 SCL Sn, (or $3 SCL 31L) derived from the bandpass filter 18 is delayed by one horizontal scanning period 1H.
  • the signals 8:, S S,, (or 8;, S S,, in a certain horizontal scanning period H and the Signal S3, SCL Sn, (of S3 SCL S,,) in the subsequent horizontal scanning period H which are respectively derived from the delay circuit 19 and the bandpass filter 18, are supplied to an adder circuit 20 to be added together therein and to provide as an output a chrominance signal 25 such as is depicted in FIG. 5D.
  • the delay in circuit 19 is one horizontal scanning period, the content of chrominance signals in adjacent horizontal scanning periods are so similar that they can be regarded as substantially the same. It is also possible to delay the signal from the bandpass filter 18 by three or five horizontal scanning periods due to the similarity of the chrominance signal contents in periods that are spaced even to that extent.
  • the index signal -2S, (or 28,) thus obtained is reversed in phase at every horizontal scanning period
  • Reference numeral 23 identifies a change-over switch which is preferably an electronic switch in practice. Such switch is shown to have fixed contacts 23a and 23b and a movable contact 230. The output of the limiter 22 is directly connected to one fixed contact 23a of the change-over switch 23 and is connected to the other fixed contact 23b through an inverter 24.
  • the change-over switch 23 is arranged so that its movable contact 230 makes contact with the fixed contacts 23a and 23b alternately in successive horizontal scanning periods in synchronism with the alternating signal S, impressed on the primary winding 12a of the transformer 12 to thereby derive the index signal 2S, from the movable contact 23c at all times.
  • the chrominance signal S derived from the adder circuit 20 is supplied to each of three synchronous detectors 25,26 and 27.
  • the index signal S is supplied to the synchronous detector 25 through a phase shifter 28 which adjusts the phase of the index signal to the axis of the red signal in order to produce a color difference signal R-Y at the output of the detector 25.
  • the output signal from the phase shifter 28 is supplied to the synchronous detector 26 through a phase shifter 29 to produce a color difference signal G-Y at the output of the detector 26 and the output signal from the phase shifter 29 is supplied to the synchronous detector 27 through the phase shifter 30 to produce a color difference signal B-Y at the output of the detector 27.
  • the phase shifters 29 and 30 each change the phase of the input signals by 120.
  • These color difference signals R-Y, G-Y and B-Y and the luminance signal Sy are applied to a matrix circuit 31 which provides color signals S S and S at T T and T respectively.
  • the color signals thus obtained may be suitably processed to produce color television signals for the NTSC system and other various systems.
  • the color filter F is disposed within the image pickup tube 2 for the formation of the color separated images on the photoconductive layer 1, but it is also possible to project a color separated pattern of the object on the photoconductive layer by using a conventional optical system.
  • the electrodes A and B can be formed, for example by the steps depicted in FIGS. 7A and 7B.
  • the first step is the formation, on one surface of an insulating plate 101, of a transparent conductive layer 102, for example, of tin oxide including antimony.
  • a transparent insulating layer 103 for example, of silicon dioxide, and a transparent conductive layer 104 similar to the layer 102 are sequentially formed over the entire area of the transparent conductive layer 102.
  • a photoresist material such as KPR (trademark) is coated over the entire area of the layer 104 and exposed to light through a mask having a predetermined pattern, and thereafter the photoresist material is developed to provide an etching mask 105 having the predetermined pattern, as shown in FIG. 7A.
  • unnecessary exposed portions of the transparent conductive layer 104 and the insulating layer 103 are etched away to provide the electrodes A and B by means of the exposed portions of layer 102 and the remaining portions of layer 104, as depicted in FIG. 7B.
  • the etching operation may be achieved with two steps, that is, the overall structure may be immersed in one etchant for selectively etching away the conductive layer 104 and then in another etchant for selectively etching away the insulating layer 103.
  • the conductive layer 104 and the insulating layer 103 to be etched away can be removed simultaneously by selectively etching away the insulating layer 103 of silicon dioxide through the conductive layer 104 using an etchant composed of, for example, a mixture of fluoric acid with antimony fluoride. The latter method requires only one etching process.
  • the respective color signals can be picked up without crosstalk therebetween and the index signal for color separation can also be obtained with ease to ensure separation of the respective color signals.
  • the index signal is not produced optically as previously described, and this leads to simplification of the optical system used and an increase in the rate of utilization of light to provide an increased dynamic range of the photoconductive layer.
  • the photoconductive layer 1 makes contact with either of the electrodes A and B over the entire area of the photoconductive layer. Accordingly, photoelectric conversion is achieved all over the photoconductive layer to provide for uniform photoelectric conversion efficiency over the entire area thereof. This eliminates the possibility that the absence of the electrode at one portion of the photoconductive layer may lead to loss of the signal component corresponding to the color at that portion with consequently reduced color fidelity. Therefore, complete white balance is always obtained and the signal to noise ratio is enhanced.
  • the electrodes A and B are formed of the same material, the condition of the boundary between the electrodes A and B and the photoconductive layer 1 is uniform throughout. Further, the electrodes can be readily formed by etching as previously described and the portions to be etched away are relatively wide and hence can be accurately etched away with ease in the making thereof.
  • the stripe electrode B and the insulating layer 5 are coupled together at both ends as a unitary structure, as shown on FIG. 3, so as to ensure mechanical and electrical connection of the electrode B even when one or more of the stripe electrodes B, is cracked by some cause in the manufacturing process.
  • a color television camera comprising image pickup means having a first continuous transparent conductive layer, a plurality of insulator layers formed on spaced apart, stripe-like areas of said first conductive layer, a plurality of second transparent conductive layers which are stripe-like and formed on said insulating layers to be separated by the latter from said first transparent conductive layer and a photoconductive layer formed over said first and second conductive layers and contacting all of said second conductive layers and said first conductive layer between said insulator layers, filter means disposed between an object to be televised and said photoconductive layer to form a first color video image on said photoconductive layer in accordance with the color components of said object, and circuit means for supplying voltages to said first and second conductive layers to form electrically on said photoconductive layer a second index image which is in overlapping relation to said first image to indicate the relationship between said color components of said object.
  • each second conductive layer is equal to the width of the respective insulator layer.
  • a color picture pickup tube for a color television camera comprising electron beam generating means, a transparent plate, a first continuous transparent conductive layer on said transparent plate, a plurality of spaced apart, stripe-like insulator layers on said first transparent conductive layer, a plurality of stripe-like second transparent conductive layers on said insulator layers to be electrically separated by the latter from said first conductive layer, means for electrically connecting said second transparent conductive layers to each other, a photoconductive layer formed on said second transparent conductive layers and on the areas of said first conductive layer between said insulator layers, and connecting means for said first and second transparent conductive layers, respectively.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Color Television Image Signal Generators (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US137334A 1970-04-29 1971-04-26 Color television camera Expired - Lifetime US3688023A (en)

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JP45036661A JPS5014490B1 (enrdf_load_stackoverflow) 1970-04-29 1970-04-29

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US (1) US3688023A (enrdf_load_stackoverflow)
JP (1) JPS5014490B1 (enrdf_load_stackoverflow)
CA (1) CA943237A (enrdf_load_stackoverflow)
DE (1) DE2120982A1 (enrdf_load_stackoverflow)
FR (1) FR2086468B1 (enrdf_load_stackoverflow)
GB (1) GB1332592A (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3754097A (en) * 1971-11-17 1973-08-21 Sony Corp Color television camera
US3813490A (en) * 1971-10-08 1974-05-28 Emi Ltd Colour television cameras
US3816848A (en) * 1972-03-29 1974-06-11 Magnavox Co Automatic focus control for image pickup devices

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS52127902U (enrdf_load_stackoverflow) * 1976-03-24 1977-09-29

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2843659A (en) * 1950-12-23 1958-07-15 Emi Ltd Color television apparatus

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB743156A (en) * 1953-09-19 1956-01-11 Emi Ltd Improvements relating to colour television apparatus
US2848358A (en) * 1955-03-24 1958-08-19 Rca Corp Method of making ray sensitive targets
NL295874A (enrdf_load_stackoverflow) * 1962-07-26

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2843659A (en) * 1950-12-23 1958-07-15 Emi Ltd Color television apparatus

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3813490A (en) * 1971-10-08 1974-05-28 Emi Ltd Colour television cameras
US3754097A (en) * 1971-11-17 1973-08-21 Sony Corp Color television camera
US3816848A (en) * 1972-03-29 1974-06-11 Magnavox Co Automatic focus control for image pickup devices

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Publication number Publication date
FR2086468A1 (enrdf_load_stackoverflow) 1971-12-31
DE2120982A1 (de) 1971-11-18
JPS5014490B1 (enrdf_load_stackoverflow) 1975-05-28
GB1332592A (en) 1973-10-03
CA943237A (en) 1974-03-05
FR2086468B1 (enrdf_load_stackoverflow) 1975-04-18

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